Tourism probably started in Roman times. Rich Romans visited friends and family who were working in another part of the Roman empire. But when the empire broke down, this kind of tourism stopped.

    In the early 17th century, the idea of the “Grand Tour” was born. Rich young English people sailed across the English Channel（英吉利海峡）. They visited the most beautiful and important European cities of the time, including Paris in France, and Rome and Venice（威尼斯）in Italy. Their tours lasted for two to four years, and the tourists stayed a few weeks or months in each city. The “Grand Tour” was an important part of young people's education—but only for the rich.

    In the 18th century, tourism began to change. For example, people in the UK started to visit some towns, such as Bath to “take the waters”. They believed that the water there was good for their health. So large and expensive hotels were built in these towns.

    In the 19th century, travel became much more popular and faster. When the first railways were built in the 1820s, it was easier for people to travel between towns, so they started to go for holidays by the sea. And some started to have holidays in the countryside as cities became larger, noisier and dirtier.

    Traveling by sea also became faster and safer when the first steamships were built. People began to travel more to far-away countries.

    The 20th century saw cars become more and more popular among ordinary people. Planes were made larger, so ticket prices dropped and more people used them.

    Thus tourism grew. In 1949, Russian journalist Vladimir Raitz started a company called Horizon Holidays. The company organizes everything—plane tickets, hotel rooms, even food—and tourists pay for it all before they leave home. The package tour and modern tourist industry was born.

    The first travel agency in China was set up as early as 1949. But tourism did not take off until 1978. In 2002, the industry was worth 500 billion Yuan and became an important part of China's social development.

    Tears ran down from my eyes as I saw the essay my high school English teacher had just handed back. A big F was written on top. I was hopeless. I was stupid !My face burned with shame when my classmates called me stupid.

    “I'm the only one who doesn't know my ABCs!” I sobbed to Mom.

    “I'll help,” she promised.

    Everyday I sat with her, but to me, cat looked like cta and red was reb. Frustrated, I would return to my bedroom and draw, filling the paper with houses, restaurants and offices.

    “When I grow up, I want my own store,” I told Mom , pointing to my drawings.

    “That's great!” she said, “ but first you have to learn to read.”

Later, I was diagnosed with dyslexia (失读症). So Mom took me to a learning centre, where I was given reading exercises. But I still had a hard time. Finally, I graduated, but I was afraid of my reading skills.

    “I'll never get a job !”  I cried to Mom later again.

    “Don't focus on what you can't do,” she comforted, “ Concentrate on what you really can.”

    But what can I do? I wondered. Suddenly, I thought of the drawings I'd made as a child and my dream of having my own store. I enjoyed sales so much that over the next few years, I tried my hand at other businesses. Today, I watch over seven branches. We have 187 employees and $15 million in sales.

    While I'll never be what my teachers might have wanted, I am a success--on my own terms. The other day a student sent me a card, reading: You gave me so much confidence. I hope to be like you when I am big. Tears of joy filled my eyes. This was my A, and I smiled.

    British chemist David Evans has become an overnight celebrity on Chinese social media. His chemistry experiments have attracted over 2 million followers in just a few months. Evans is a chemistry professor at the Beijing University of Chemical Technology. The 60-year-old always wears a white lab coat, a pair of safety goggles (护目镜), and smiles often. Some web users say he looks just like the “grandpa of KFC”.

    Evans has posted videos of various experiments. His most popular experiments have attracted millions of hits on video-sharing apps. Excited children's cheers and shouts can be heard in his videos. “I hope my experiments can arouse people's interest in science,” he says.

    Evans has been interested in China since childhood. In the early 1970s, before the reform and opening-up, he viewed it as a “country full of mysteries”. He first visited the Chinese mainland in 1987 to attend a chemistry conference in Nanjing, Jiangsu Province. He quit his job in the United Kingdom and moved to Beijing in 1996. Many of his friends thought he was crazy. But Evans says they just saw China's challenges but not its potential.

    Since 2011, Evans has turned to the Internet to popularize science. He learned short-video apps are also popular in small cities and rural areas. And he realized this enables him to reach more students, who lack opportunities to perform fun experiments. But even a one-minute video requires a considerable amount of work. Still, he thinks it's worth it to fulfill his responsibility to popularize science.

    His experiments always fill schools' lecture halls with laughter. Some viewers call him “a Harry Potter-like magician”, but he disagrees. “A magician never tells the secrets behind his tricks, but a scientist always gives an explanation.” He sees himself as a teacher. He performs experiments to spread knowledge, inspire thinking, remove misunderstandings and show that science can create change. Evans says he looks forward to more “chemical reactions” with China.

    Did you know that badminton is also a fast-paced competitive sport? Badminton has been a Summer Olympic sport since 1992. Para-badminton will be included in the 2020 Summer Olympic Games in Tokyo. Here's what you need to know if your child is interested in badminton.

    Badminton is played on a 44-foot-long rectangular (矩形的) court that is 17 feet wide for singles and 20 feet wide for doubles. It is divided in the middle by a net placed 5 feet off the ground, like volleyball, not at ground level like tennis.

    In competition, each match is a set of three games played to 21 points. There is a one-minute break when a player or team reaches 11 points, and a two-minute break in between the first and second games and the second and third games.

    Age kids can start: About 6 years old.

    Best for kids who: Have good skills, are patient and hardworking, and can handle the pressure of one-on-one or two-on-two competition.

    Team or individual: Matches can be singles (one-on-one) or doubles (two-on-two).

    Fun fact: Badminton is the only sport that has mixed doubles event in the Olympic Games.

    Costs: Beginners are expected to pay $30 to $40 for an entry-level racket (球拍). Badminton shoes are similar in price to other athletic shoes. Join a club or team for lessons and court time. A one-hour group lesson for beginners should cost $20 to $25, with costs increasing as your child moves up the ranks. You will also pay entry fees for competitions.

    Time commitment required: Beginners will play for just an hour or two per week.

Potential for injury: Players have a very low risk of injury. Players who wear glasses should use eye protection.

    While staring out of the window during a flight, not everyone will think carefully about the question why airplanes have rounded windows rather than square ones.

    Over the years, aerospace engineering has made huge steps in airplane technology, meaning planes can carry more passengers and go faster. The planes have also changed shape to increase safety—including the windows. As commercial air travel took off in the mid－20th century, airline companies began to fly at higher altitudes to lower their cost—the air density(密度) is lower up there, creating less drag(阻力)for airplanes. However, higher altitudes came with problems, like the fact human beings can't really survive at 30，000 feet. To make that possible, the cabin was changed to a cylindrical(圆柱体) shape to support the pressure inside. But at first, plane builders left in the standard square windows and this expansion meant disaster. The de Havilland Comet came into fashion in the 1950s. With a closed cabin, it was able to go higher and faster than other aircraft.

    However, where there's a corner, there's a weak spot. Windows, having four corners, have four potential weak spots, making them likely to crash under stress—such as air pressure. By curving the window, the stress that would eventually break the window corner is distributed and the chance of it breaking is reduced. Rounded shapes are also stronger and resist deformation(变形), and can thus survive the extreme differences in pressure between the inside and outside of the aircraft.

    Fortunately, designers figured out the lack of design pretty quick. Now we have nice, rounded airplane windows that can resist the pressure of traveling altitude. It gives being able to gaze out of your window to the world from 35，000 feet a whole new outlook, doesn't it?

    Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri (MU) researchers are developing a nuclear energy source that is smaller, lighter and more efficient.

    "To provide enough power, we need certain methods with high energy density (密度)", said Jae Kwon, assistant professor of electrical and computer engineering at MU. ''The radioisotope (放射性同位素) battery can provide power density that is much higher than chemical batteries."

    Kwon and his research team have been working on building a small nuclear battery, presently the size and thickness of a penny, intended to power various micro systems (MNEMS). Although nuclear batteries can cause concerns, Kwon said they are safe.

    "People hear the word 'nuclear' and think of something very dangerous." he said. "However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems."

    His new idea is not only in the battery's size, but also in its semiconductor (半导体). Kwon's battery uses a liquid semi conduct or rather than a solid semiconductor.

    "The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure (晶体结构) of the solid semiconductor." Kwon said, "By using a liquid semiconductor, we believe we can minimize that problem."

    Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, Kwon is working to build and test the battery. In the future, they hope to increase the battery's power, shrink its size and try with various other materials. Kwon said that battery could be thinner than the thickness of human hair.